This hazard zone is based on explosive eruptions from vents located along the
chain in the past 10,000 years that are known to have ejected <1 km3
(0.25 mi3) of magma and generated pyroclastic flows or surges. The zone
is centered along the south moat of the caldera, which is the location of
epicenters of many swarms of earthquakes since 1980 and the area of most intense
ground movement (deformation). Thus, scientists suggest that future eruptions
might occur from this restless zone, and pyroclastic flows and surges could travel
as far as 15 km (10 mi) from a new vent. Future pyroclastic flows and surges from
a single eruption in the south moat would affect only a part of the total hazard
zone shown on the map.